Sikorsky S-39 Build from Scratch - RC Groups
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Oct 28, 2016, 01:09 AM
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Build Log

Sikorsky S-39 Build from Scratch


Sikorsky S-39, 1/12th scale, build after Bob Rich plan

I was looking for a scale waterplane to build from scratch and after some research for a model with the right size and a nice look I saw the S-39. As a good plan from Bob Rich was available as well as build logs for this particular plane I descided to give it a try and build it. I reduced the scale from 1:8 to 1:12 which gives a wingspan of about 52" (~1.3m) and a length of about 32" (~0.8m). My target weight is around 40oz (~1.13Kg).

Here's the link to the build log, where I'll post pictures and comments about the build.

Sikorsky S-39, 1/12 scale, scratch build


To begin with, I contacted Mat who built a wonderful S-39 from the same plan but slightly bigger, and he gave me already a lot of very valuable information. Thanks so much for that. He also has a blog with lots of information about several projects he already realized.

Sikorsky S-39 build "Spirit of Africa"
Sikorsky S-39 Maiden

The build log of another fantastic S-39 from Willsonman can be found here. His model is build from foam but some helpful information can be found in his great build log.

2015 Scratch Build: Sikorsky S-39

And the build log from warhead_71 who built a foamie S-39 with 52" wingspan. Brilliant build log as well!

1:12 scale Sikorsky S-39

Cheers Jannick
Last edited by Fridolin1981; Yesterday at 12:13 AM. Reason: Sikorsky S-39 build from scratch
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Oct 28, 2016, 12:03 PM
No Hangar Queens!
http://forum.flitetest.com/showthrea...S-39&highlight

As-designed, the Bob Rich plans fly very well. By far my favorite airplane in my hangar. As your will be smaller I highly suggest you keep it light. I built at the full 76" span and it needed at least a 4500mAh 4S battery to balance out. For sure let me know if you have a question about anything. I spent a year planning the build, then built it to flying condition in 3.5 days. You will love the end result.
Oct 30, 2016, 03:42 AM
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Lovely build Willsonman! Weight is pretty much my biggest concern. I know from Mat that with a WS of about 54" and 44.8 oz (1.27Kg ) of weight the bird flies really great :-) So I guess with 52" and hopefully about 40 oz would be fine. We'll see if that will work out
Thanks for the offer, there will definitely be quite a few questions coming up.

Cheers Jannick
Nov 08, 2016, 03:44 AM
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Some progress on the CAD model of the S-39


I found some spare time to make some progess on the CAD model of the S-39. I added the tail booms with sheeting and the horizontal stabilizer. It took me a while to figure out a way to fix the booms which I intend to build from carbon rods, and sheet them.

Cheers Jannick
Nov 30, 2016, 12:57 AM
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Hi Jannick,
I'm pleased to see you have made a start!
The CAD work looks great and your boom attachment looks reasonably similar to how I did mine.

Keep up the good work and I'm looking forward to seeing yours fly.

Willsonman, I hadn't seen your version before, fantastic build! I'll be going through your thread and having a good read when I've got a bit of time to go through the 35 pages!

-Mat-
Nov 30, 2016, 05:21 AM
No Hangar Queens!
Its a long read as I planned the build for nearly a year, only to do the bulk of the build over 3.5 days at Flite Fest. It sure was odd going to a multi-day event with NO flying aircraft but when Flite Test provides two 40x100' tents to build under, you kind of want to take advantage of that when you love to build as much as I do.
Dec 08, 2016, 04:43 AM
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Hey Mat,

The wing model is nearly finished, took me quite some time, to make sure all fits together including servos, linkages and the pull-pull wires for the rudder and elevator.
Now I built a good part of the hull, it seems reasonably easy to assemble. The sheeting won'be that easy I guess :-)

Cheers Jannick
Dec 09, 2016, 04:14 PM
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The sheeting is not too bad, most of it is simple curves. The only tricky bits are the top of the cabin and the battery hatch. The cabin i strip planked and the hatch i just made from Blue foam, which has the added bonus of being positively buoyant if it comes loose.

Remember that when you sheet the hull grain goes from keel to chine not front to back
Dec 16, 2016, 04:20 AM
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Progress on CAD Model


I managed to make some progress on the CAD model. The struts seem to be great fun, as each one is different... But fortunately it is much easier to bend the brass inserts in real than on the CAD model :-)

Cheers Jannick
Jan 21, 2017, 10:34 AM
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Finally the order for the wood is placed. As there are quite a lot of different types of wood with different thicknesses and so on, it took me a while to get everything together. Hopefully I'll find some time to start the build soon. The first steps will be cutting the parts for the hull and build it up. Looking forward to my first steps in building a model from scratch
Jan 27, 2017, 01:34 AM
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Wood has arrived


Well, the wood has arrived, now I've to buy some tools, glue and the remaining material like carbon tubes and rods. This I'll do tomorrow and then the cutting and building can begin
Feb 02, 2017, 03:30 PM
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First parts cut


After a lot of research and CAD modeling I made a start with cutting parts. The hull main crutch, the keel and formers 1&2 lower and upper part each are done It will take a while to cut all the parts But it's fun. By the way, I'm using old school tools like scalpell and a coping saw I preserved from my childhood

Cheers Jannick
Last edited by Fridolin1981; Feb 05, 2017 at 04:05 AM.
Feb 02, 2017, 08:24 PM
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Cutting the first pieces is certainly a milestone Jannick, well done.
Remember to slim down the parts wherever possible as this model was designed to cope with the stresses of combustion engine, not electric, which is much kinder on the airframe.
I notice you’ve included the slots on the crutch for all of the formers. They are fine there for the moment and you may find it nice to stabilise the hull while you sheet, but you may need to cut a few of the cross braces out to make the battery hatch. If I recall correctly the hatch on the original design is large enough for a servo, not battery access. I’ll post a photo of mine for reference.
Feb 05, 2017, 03:28 AM
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Well indeed, it feels like the real start of the project I know there are some details I could have left away, or I'll need to remove for the battery hatch. A picture as a reference would be great.
Cheers
Jannick
Last edited by Fridolin1981; Feb 07, 2017 at 07:06 AM.
Feb 05, 2017, 07:24 AM
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Sorry, Jannick, I forgot I had promised you a few photos.

These should show you what I modified around the battery hatch area

I really think I should have given her a wipe over before taking her photo

Looks like I left the front of the crutch and the first cross brace, then took out the next two.
Last edited by Wormboy; Feb 05, 2017 at 08:46 AM.

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